1,1′-bi-2-naphthol, a compound obtainable by dimerization of β-naphthol or its derivative, is useful for preparing an antiseptic compound or an asymmetric synthesis catalyst.
In addition, dimers of 2-hydroxynaphthalene-3-carboxylic acid and of 2-hydroxynaphthalene-6-caboxylic acid are useful as toning agents.
U.S. Pat. No. 3,278,610 discloses a method for preparing the above described dimers, which comprises dimerizing β-naphthol in a solvent such as benzene in the presence of copper chloride, amine and oxygen.
J. Org. Chem. 1999, 64, 2264-2271 discloses a method for dimerizing β-naphthol or the like, which comprises oxidative coupling of β-naphthol, methyl 2-hydroxynaphthalene-3-carboxylate or the like in the presence of copper(I) chloride-tetramethylethylenediamine complex in dichloromethane, wherein copper(I) chloride and tetramethylethylene diamine are combined before the coupling reaction.